Anyone ever seen a Dempsey with a nuchal hump?

[puffers4puffers]

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In the book "Cichlids from Central America" by Ad Konings, he posits an interesting theory.
That a successful spawn in nature occurs, when only 1 individual (of say 1,000 eggs) survives to maturity.
And he uses Parachromis managuense in one of the Nicraguan lakes as his theoretical test subject.
Its no surprise, young fish are preyed upon by everything from insects, and crustaceans, to small birds.
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The catfish above, being eaten by the shrimp is about 3" - 4"
The larger the fish get, to a certain point, the smaller their pool of predators become.
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In aquariums managuense size norm might average only 10-12" , and I have seen some aquarists poo poo the idea that under the right they can easily hit 18 to 20 inches.
But I have had some in my tanks, easily hit 16"and not be done growing, and the record for hook and line fishing is 22"

Great book!

 

[neutrino]

In the book "Cichlids from Central America" by Ad Konings, he posits an interesting theory.
That a successful spawn in nature occurs, when only 1 individual (of say 1,000 eggs) survives to maturity.
And he uses Parachromis managuense in one of the Nicraguan lakes as his theoretical test subject.
Its no surprise, young fish are preyed upon by everything from insects, and crustaceans, to small birds.

I can't say I've specifically researched this in science literature, but I suspect that (along with numbers of eggs produced) spawning age may tell you something about survival to adult rate, which is to say I suspect species that spawn at 6 months and half their adult size likely have lower survival to older ages and full potential sizes than slower maturing species that may not reproduce until 2, 3 years of age and closer to max size.

The thing about some size references in taxonomic descriptions is they can be based on limited numbers collected or collected from a limited area or even a single location. Populations from other locations might vary in size for various reasons, whether it's their genetics, differences in water temperature or chemistry, differences in food available, heavily or sparsely fished or collected or whatever else. In fact, as I expect you know, different populations of the same species can tend to reach different sizes in an aquarium-- as well as having color differences.

 

[Hybridfish7]

That's funny. A couple of days ago someone (else) told me JDs (among some other species) "tend to get eaten by things once they hit the 5" mark" as an argument that said species (including JDs) are mostly in the 5-6 inch range-- I could have gotten into a debate, but I was busy with more important things... and I'm getting too old to debate every opinion I disagree with.

Take it up with duanes, I got the "fish of that niche usually get eaten before they can hit a certain size" thing from him. And I still don't think you understood what I was saying.

 

[neutrino]

Take it up with duanes, I got the "fish of that niche usually get eaten before they can hit a certain size" thing from him. And I still don't think you understood what I was saying.

I have been.

While that's true of most fish species (not just a certain niche) if translated to percentages surviving to become breeding adults or older, my point was it doesn't define the size limit of wild fish or prove that Aequidens in the wild can only reach 5 inches.

 

[Hybridfish7]

I have been.

While that's true of most fish species (not just a certain niche) if translated to percentages surviving to become breeding adults or older, my point was it doesn't define the size limit of wild fish or prove that Aequidens in the wild can only reach 5 inches.

I never said that they can't, I was saying how they don't most of the time, but I believe you've gotten enough of that from Duanes already